As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYS - IN LEVEL FLIGHT (2.5 ANU), THE STANDBY ATTITUDE INDICATOR SLOWLY PRECESSES - 20 DEG RT BANK/10 DEG ANU AT THIS TIME. INSTRUMENT IS ILLUMINATED. NO FLAGS, CAGED IT AND IT HAPPENED AGAIN. REPLACED STBY ATT INDICATOR OPS CHECK OK IAW MM 34-25-01.